While an information terminal apparatus is rapidly becoming thinner, smaller, and more multifunctional, a semiconductor which is mounted thereon is also demanded to become further thinner and to have higher density. In order to make the device further thinner, it is also demanded to make a semiconductor wafer on which the semiconductor is integrated further thinner. Therefore, the backside of the semiconductor wafer is often ground and made thinner.
In addition, a bump (or electrode) formed of solder or the like is formed on the front face of the wafer, and unevenness is frequently provided thereon. When such a bump-provided semiconductor wafer is subjected to back grinding, in order to protect the front face that has bump portions, a semiconductor processing sheet is stuck onto the front face of the wafer. Hitherto, as the semiconductor processing sheet, it is general to use a pressure sensitive adhesive sheet including a base material and a pressure sensitive adhesive layer provided on one surface of the base material.
In order to appropriately protect the uneven portions, such as bumps, etc., existing on the front face of the wafer, the aforementioned semiconductor processing sheet is demanded to have embedding properties to a bump or followability to unevenness. In addition, if the pressure sensitive adhesive of the semiconductor processing sheet remains in the unevenness, a fault is liable to be generated in the semiconductor device due to a residue of the pressure sensitive adhesive. Therefore, for example, PTL 1 discloses that in order to suppress the residue of the pressure sensitive adhesive in the unevenness while increasing the followability to unevenness, in the semiconductor processing sheet, an intermediate layer and a pressure sensitive adhesive layer are provided on a base material, and the intermediate layer and the pressure adhesive layer are each formed of a specified acrylic polymer.